A heat sink with incorporated pin fin arrangement means is preferably part of a cooling jacket assembly, used for cooling the electric machine assembly. In general, the cooling jacket assembly comprises an annular cooling jacket body (i.e. a heat sink (4)) preferably adapted for receiving a stator (3) of the electric machine. In addition, the heat sink (4) of a cooling jacket comprises at least one substantially cylindrical wall section with at least one group of incorporated unidirectional heat transfer protuberances (i.e. pin fin (42) arrangement in free-form formation), wherein the heat sink (4) in cooperation with the electric machine assembly forms an annular gap (i.e. a cooling channel) preferably adapted for coolant flow circulation. The heat sink (4) according to the invention is preferably casted or molded as one body part in a single operation; hence the cost effective solution of high performance heat sink (2) is achieved.